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[aprssig] WRT54G APRS Project

n5oom at arrl.net n5oom at arrl.net
Wed Feb 9 06:35:12 UTC 2005


The North Texas Microwave Society HSMM (High Speed MultiMedia) 
working group is looking at the various ham applications for HSMM 
technologies.  One of the interesting things to pop up that has a 
direct APRS application is the Linksys WRT54G router.

The WRT54G, and a few other manufacturer's models with similar 
hardware, are in fact small linux based computers.  Various groups 
have developed third-party firmware updates for it, exposing more 
features.  In addition, the box has a couple of serial ports which 
may be accessed by soldering a header strip to some unused pads on 
the circuit board and adding a cheap RS-232 level converter.  Add a 
TNC (say, a TNC-X) and some software and we should have a cheap, 
reprogrammable digi and internet gateway with wireless bridging 
capability.

Talking to AE5PL the other day about the inefficiencies of routing 
APRS packets, the discussion turned to the difficulties of routing 
traffic between digis via RF, and the benefits of routing traffic 
between digis via internet gateways.  Simply, it would allow APRS 
operators to use software to more finely control traffic than is 
possible given the fixed code in the KPC-3.

The drawbacks to this plan are:
1.  Digi traffic would be exposed to internet failures
2.  While eliminating cross-digi RF traffic would free up more air 
time for user stations, the digi to internet gateway traffic would 
suck up more air time.
3.  Each internet gateway would require an internet connection, which
may not be feasible in all areas.

Enter the WRT54G based digi. This would allow the digi / internet 
gateway to be consolidated in one box, mounted at a location where RF 
coverage is best, and an internet connection wirelessly bridged to 
the digi location.  

Also, because the APRS firmware would be housed 
in non-volatile ram, digi and gateway rules could be dynamically 
changed to suit conditions, something that is impossible with a KPC-3 
based system.  

This plays into emcomm applications as well.  My county ARES group is 
looking strongly at Winlink to provide us with a county-wide email 
service.  In this case, access to the  Winlink email service would be 
provided via 2m packet Telpac stations.  In an emergency situation, a 
WRT Digi could be dynamically converted over to a Telpac station, 
connected to the Winlink server via it's bridged wireless internet 
connection. 

To make this happen, we're looking for people with TNC experience who 
are interested in working in linux in a single board computer 
environment.  If anybody is interested in working on this project, 
please feel free to join the NTMS-HSMM working group list at:
http://groups.yahoo.com/group/ntms-hsmm/

Additional information is available at:
http://www.arrl.org/hsmm/
http://www.n5oom.org/hsmm/index.htm






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